In order to achieve a high pixel per inch (PPI) and a high production capacity, it is necessary to reduce sizes of TFTs and reduce the number of masks used in the process of manufacturing the TFTs. At present, the process of manufacturing a TFT array substrate includes processes of using 7 masks, 6 masks, 5 masks and 4 masks. It may be understood that, the fewer the masks used in the manufacturing process of the TFT array substrate, the lower the cost thereof will be.